The invention relates generally to heat exchange devices for heating and/or cooling of the human body, and more particularly to a patient therapy heat exchange structure for placing against or for being worn on the human body. The heat exchange structure can be in combination with a cooperating portable device, which may be in the form of a wheeled cart, for providing heating and/or cooling liquid to the patient therapy device at a desired temperature, with or without cyclic pressurization.
U.S. Pat. No. 4,691,762 discloses a temperature control system including a heat exchanger vest and/or helmet to be worn on the human body, accompanied by a portable unit which administers cooling to a circulated liquid which passes through the heat exchange garments. The heat exchange garments pursuant to that patent were advantageously formed as Flexitherm (a trademark of Life Support Systems, Inc.), a material, fabricated of two sheets of flexible, liquid-impervious plastic material heat sealed together to form the fluid conducting channels with appropriate manifolding.
The Flexitherm heat exchange material as constituted prior to this invention had a tendency to exhibit flow constriction problems under certain circumstances. For example, in areas where the heat exchange material was subjected to relatively sharp bends, crease lines could form in the manifolds and in the fluid conducting channels themselves due to the stresses of bending the material when pressurized with flowing liquid. These stress lines or crease lines could become deep creases and shut off flow to some flow channels and through some portions of the manifolds. The problem was accentuated further by the imbalance in pressurization shrinkage between the flow channels and the manifolds. The flow channels shrink in lateral dimension when pressurized with liquid, since the flattened channels become “inflated” to a generally cylindrical configuration, drawing the structure inward laterally. Adjacent manifolds, which are generally perpendicular to the orientation of the flow channels, shrink in the perpendicular direction, but essentially do not shrink in the direction of shrinkage of the flow channels. Upon pressurization this imbalance tended to put increased stress on the manifolds, tending to form constrictions which were even more greatly accentuated when the Flexitherm heat exchange structure was formed around curves and bends on the body.
These problems limited the usefulness of the Flexitherm material for additional therapy situations which might require relatively sharp bends and flexing situations.
Co-pending application Ser. No. 431,753, which was a division of application Ser. No. 250,778 (U.S. Pat. No. 4,884,304), disclosed a bedding system with liquid heating or cooling, wherein the liquid temperature control was provided by a mixing device which mixed warm liquid with cooled liquid as selected by the user, for maximum comfort. This provided for fast-response adjustment of temperature (and individual control in a dual control system) in the liquid flow channels of the bedding system, to quickly achieve the proper temperature for the particular user.
Such closed-loop mixing of heated and cooled liquids, to quickly achieve changes in temperature in a liquid-conducting flexible heat exchange device, was not generally available prior to the present invention. Conventional systems which have been in use have had only a single liquid tank, with the requirement of changing the temperature of water in the tank in order to achieve a change in temperature in a heat exchange device served by the tank. For example, heating/cooling devices of this general type have been available from Zero Cincinnati, Baxter Medical and Jobst.
It is an object of the present invention to provide an improved flexible heat exchange structure which may be used for thermal therapy on a patient or for other body cooling purposes, and this may be in conjunction with a portable source of heated and/or cooled liquid, and optionally air pressure, connected to the heat exchange structure or garment by fluid lines, for achieving very fast response in temperature adjustment for the patient thermal therapy.